pitting vs corrosion

pitting and corrosion both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitting	Yes	No	No	No
corrosion	Yes	No	No	No

As nouns, corrosion is a hypernym of pitting; that is, corrosion is a word with a broader meaning than pitting:

pitting: the formation of small pits in a surface as a consequence of corrosion
corrosion: erosion by chemical action

Other hypernyms of pitting include corroding, erosion.

pitting (noun)	corrosion (noun)
the formation of small pits in a surface as a consequence of corrosion	erosion by chemical action
	a state of deterioration in metals caused by oxidation or chemical action